Sharif Digital Repository

HTGRs are considered as 4th generation reactors which have prominent characteristics such as inherent safety, lower safety costs, High efficiency and high temperature applications. the most important challenges in developing these reactors is providing appropriate codes in design, simulating their performance and analysis of them. In this thesis, a japanese prismatic HTTR reactor has been selected as a reference reactor and the neurotic’s calculations implementation studied at cold zero power (CZP) and hot full power (HFP) states using DRAGON cell calculation codes and DONJON core computations. At CZP state, One group and two group radial & axial flux distribution, control rod critical... 

As a matter of fact, power systems are always faced with a variety of uncertainties. These uncertainties change system parameters in an unwanted manner which may deteriorate the system security and reliability. For instance, a transmission line which is designed for a certain capacity may be suffered as a result of load increment and consequently may influence the normal operation of other network elements. In recent years, as a result of environmental considerations and especially after the oil shock at 1973 which caused the the energy prices to increase unprecedentedly, the human has taken more attention to renewable energies exploitation. Theses energies have a fluctuating nature and are... 

In machine learning, classification is of great importance. Unlike the traditional single-label classification in which one instance can have only one label, in multi-label classification tasks, an instance can be associated with a set of labels. Multi-label classifiers have to address many problems including: considering correlations between labels, handling large-scale datasets with many instances and a large set of labels, and having only a fraction of valid label assignments in the training set. To tackle datasets with a large set of labels, recently embedding-based methods have been proposed which seek to represent the label assignments in an intermediate space. Subsequently, given the... 

The aim of this research is to examine and propose solutions for financing projects aimed at reducing vulnerability in the oil industry's infrastructure against earthquakes and enhancing their seismic resilience. Design and construction issues, as well as the gradual deterioration of oil infrastructure, increase their vulnerability to earthquakes. Earthquakes can disrupt the proper and continuous functioning of these infrastructures by causing damage. Such disruptions or interruptions in the performance of oil industry infrastructure can have significant economic and social consequences. To mitigate these damages, investment in vulnerability reduction measures is essential. Financing... 

This study consists of two parts. In the first part, the performance of the LISFLOOD-FP model, which is raster-based, and the HEC-RAS model, are compared and evaluated. This work studied different scenarios under various digital models in two study areas, the Kashkan study basin with mountainous topography and the basin in Nebraska, which has a plain surface. The flood events are among the most severe floods in both study areas that occurred in March and April 2019. This study showed that in mountain topography, the performance of both models is good even with the 30 m high digital models. Although two models perform well, in the Nebraska basin, the performance of the two models in the... 

This study opens up new horizons in data-driven structural identification methods offering extensive improvements over the existing time-/frequency-domain probabilistic methods. It pushes forward a holistic Bayesian statistical framework to integrate the existing formulations under a hierarchical setting aiming to quantify both the identification precision and the ensemble variability prompted due to model errors. Since the computation of the posterior distributions in hierarchical models is expensive and cumbersome, novel marginalization strategies, asymptotic approximations, and maximum a posteriori estimations are proposed offering mathematical formulations for the uncertainty... 

The objective of this thesis is to evaluate and calibrate design load combinations of steel building structures of Iran based on the reliability theory. The importance of this research stems from recognition that the design load combinations for steel structures in Section 6 of the National Building Code of Iran have been completely adopted from the ASCE/SEI 7-10 standard, whereas the factors that affect these load combinations differ in Iran from those of the United States. Examples are the difference in the construction industry economy, lower quality of here and the differences in probability distributions for the specifications of steel. Hence, the load combinations need to be calibrated... 

In this research, probability distribution of structural demand is estimated using a simplified dynamic analysis which is named Endurance Time method. In this method, the structure is subjected to nonlinear dynamic time history analysis, which its acceleration increases in time. It can be extracted the median of structural demand for earthquakes with different return periods. In customary researches, this estimation is performed using Incremental Dynamic Analysis knowns as IDA. The significant computational effort of IDA is the dominant obstacle that researchers and engineers encounter with. The main advantage of Endurance Time method is the fast estimation of structural demands by reducing... 

The purpose of this study is to provide a simply applicable method for accurately determining the distribution of seismic responses of structures based on the Endurance-Time Analysis. This distribution is one of the pillars of the probabilistic Performance-based design of structures. In general, the Incremental Dynamic Analysis provides the most accurate results in this regard. However, the enormous computational cost of this kind of analysis makes it practicality questionable. In an Endurance-Time Analysis, the structure is analyzed under a limited number of special acceleration excitations functions. These excitations functions are specifically designed to apply an incremental seismic... 

This thesis targets the multidisciplinary area of time-variant seismic risk analysis of transportation networks. For this purpose, a new methodology and a library of probabilistic models are developed. Risk, in this context, denotes the probability of exceeding the sum of direct and indirect losses due to seismic events. Direct economic losses are due to the repair cost of the physical damage in the components of the network, such as bridges. The indirect losses are due to the reduced capacity of the components for traffic flow, which results in increased travel times in the network. This leads to socioeconomic losses. In this research, a reliability-based approach is adopted to carry out... 

The necessity of providing synthetic acceleration records suitable for seismic assessment of the structures in the regions whose seismological history has not enough instrumental recordings has become one of the main concerns of the earthquake engineers. Despite being accurate in estimating earthquake ground motion, physics-based methods involve complicated procedures and need the detailed information about source, path and the site conditions of the scenario event which is not available for lots of engineering problems. The main goal of this dissertation is to introduce a novel stochastic method for the simulation of the non-stationary earthquake acceleration records compatible enough with... 

Damage detection and rehabiltation is one of the most economical methods of increasing safety and service life of the structures. In this research, a wave-based methodology is introduced for laminar damage location in single axial members and combined axial-flexural members within a structure. Laminar damage is a kind of local damage in which the cross section area of a member decreases within a specific length. In the proposed wave-based methodology, a structure with a laminar damage is analyzed using a Finite Element (FE) software under a high frequency loading, and the strain values in specific points of the structure is collected. Thereafter, using the wave propagation theories and the... 

The objective of this thesis is to prioritize a portfolio of buildings for seismic retrofit. A new set of sensitivity measures is proposed to rank the buildings in accordance with the reduction in the loss of the entire portfolio. To this end, various risk measures are differentiated with respect to the cost of retrofit for each building. These risk measures are the moments of the portfolio cost probability distribution which imply the risk-neutral and risk-averse decision making. Two costs are considered: Construction cost due to retrofit and repair cost due to structural and non-structural damage. To quantify the risk, reliability methods are employed in which many interacting... 

Bridges are among the crucial elements of transportation networks, and play an important role in facilitating emergency relief efforts following earthquakes. For this reason, it is emparative to monitor their damages to ensure about their performace in earthquakes. The structure of a bridge is divided into two parts, namely the superstructure and substructure. Due to the relatively high rigidity and strength of superstructures, most of structural damage is usually concentrated in substructures, which may ultimately affect the overall stability of the bridge. Therefore, assessing the level of damage in the substructure is of utmost concern. This research attempts to evaluate the damage in the... 

The process of deregulation that has involved electricity many markets has introduced several new interesting research topics in power system area. This thesis addresses one of the most fascinating issues among them: the study of distributed generation both renewable and conventional integration in distribution networks. From the distribution network operator (DNO)'s point of view, it is of interest to develop a comprehensive methodology which considers various distributed generation technologies as an option for supplying the demand in distribution networks. In this thesis, the planning problem has been multi-objectively modeled. This will help the planner in decision making while knowing... 

Graph Theory and Combinatorial Analysis like the other branches of science use the probability for solving their problems. At the first , we will introduce the most common tools from probability used in Discrete Mathematics, such as “The Lovasz Local Lemma”. Most of them are based on Linearity of Expectation, Concentration Theorems and some other innovative methods such as Deletation Method. We will present different examples for these techniques. Also we will introduce “Random Graphs” and their importance. Specially we will explain how to use “Threshold Functions” to obtain different properties about the majority of graphs. Rainbow Connection, is a natural and interesting quantifiable way...